System and method for measuring per node packet loss in a wireless network

ABSTRACT

A method and system for configuring a wireless network, e.g., an ad hoc wireless network having a plurality of nodes and at least one server. In the wireless network, among other things, mesh network viability is maintained as packet loss information is recorded at a plurality of individual nodes in the wireless network during packet transmission from each of the plurality of nodes. The packet loss information may be stored at the at least one server for access at a period of time other than the moment when the packet is received at the at least one server from one of the plurality of nodes.

BACKGROUND

1. Technical Field

Specific matter disclosed herein relates to the field of wirelessnetworks.

2. Background Information and Description of Related Art

Advancements in technology have enabled small, wireless devices tointeract with one another to form wireless networks, e.g., mesh ormanaged networks and ad hoc wireless networks. An ad hoc wirelessnetwork, as compared to a managed network, is a wireless network inwhich wireless communications occur directly between wirelesscommunication devices such as a peer to peer network without a managednode, e.g., between laptops or other wireless devices. A managedwireless network is the type of network that is found in a specificlocation such as a coffee shop or at a wireless access point of a homenetwork, i.e., a “hotspot.”

Wireless devices such as the wireless devices of an ad hoc network canbe deployed in various environments where a wired network would not befeasible, such as an unwired industrial area. By establishing an ad hocnetwork in such an environment, the total cost of ownership associatedwith a network can be reduced by eliminating the need for wiring.Testing of wireless networks may be desired for, among other things,testing of packet loss when the packets are transmitted from node tonode across a communication link. However, current test methodologiesfor networks, such as Ethernet (versions of IEEE Std. 802.3), are lessuseful in an ad hoc wireless network, where each node in the network mayhave different packet loss characteristics.

For example, current test methodologies incorporate endpoints in thenetwork and assume a reliable medium for measuring test results across anetwork. Existing test systems ignore the fact that each node of awireless ad hoc network may have different packet loss characteristicsbecause the transmission medium is often inconsistent from point topoint. Thus, it would be desirable to measure the per node packet lossat each node in a wireless network in order to determine the overallmesh network viability.

In some wireless networks, it is desirable to measure network viability.Mesh network viability is measured with endpoint nodes and per nodepacket loss. The term “per node packet loss” as referred to hereinrefers to the packet loss per node in a wireless network. The term“endpoint node” as referred to herein refers to a node of a wirelessnetwork that is used in the calculation of packet loss in a wirelessnetwork. The term “mesh network viability” as referred to hereinrepresents the cumulative packet loss of the overall network, i.e.,packet loss for all nodes of the wireless network, versus the singlenode packet loss generation of a wireless network endpoint node.

Because a number of the existing wireless technologies are batterypowered, packet loss may be a drain on the batteries. One source ofbattery drain is the re-transmission of lost packets. In a wirelessnetwork, it is possible for network topology to create excessive packetloss between nodes in the wireless network because, for example, anobstruction is present or introduced between two nodes, or excessivenetwork packet traffic is using a particular node to carry out networkcommunications between a node and a server.

For example, if three nodes in a wireless network are routing packetsthrough a single node, that node may be overloaded. Because the node isoverloaded, a significant number of the packets from that portion of thenetwork may be lost. Depending on where the test endpoint is placed inthe network, the current methodologies for testing network packet lossmay not see this issue. If the endpoint is placed in such a way that theoverloaded node is not part of the test, the test may report that thelink/node has a low packet loss and therefore the network has a lowpacket loss in general, and as such, erroneously so, may be assumed asnot needing servicing. Examples of routing protocols that run ontechnologies that can be battery powered are DSDV (Destination-Sequenceddistance Vectoring) and AODV (Ad Hoc On Demand Vectoring).

Many other problems and disadvantages of the prior art will becomeapparent to one skilled in the art after comparing such prior art withthe present invention as described herein.

BRIEF DESCRIPTION OF DRAWINGS

The invention may best be understood by referring to the followingdescription and accompanying drawings that are used to illustrateembodiments of the invention. In the drawings:

FIG. 1 illustrates a wireless network of nodes and a server operatingaccording to an exemplary embodiment of the present invention.

FIG. 2 illustrates one embodiment of packet flow in a server accordingto the wireless network of FIG. 1.

DETAILED DESCRIPTION

In the following description, specific matter disclosed herein relatesto the field of wireless networks for a system and method for measuringper-node packet loss in a wireless network. Specific details ofexemplary embodiments of the present invention are set forth. However,it is understood that embodiments of the invention may be practicedwithout these specific details. In other instances, well-known circuits,structures and techniques have not been shown in detail in order not toobscure the understanding of this description.

The term “memory medium” is intended to include an installation medium,e.g., a CD-ROM, floppy disks, or tape device; a computer system memoryor random access memory such as DRAM, SRAM, EDO RAM, Rambus RAM, etc.;or a non-volatile memory such as a magnetic media, e.g., a hard drive,flash, or optical storage. The memory medium may comprise other types ofmemory as well, or combinations thereof. In addition, the memory mediummay be located in a first computer in which the programs are executed,or may be located in a second different computer which connects to thefirst computer over a network, such as the Internet. In the latterinstance, the second computer may provide program instructions to thefirst computer for execution. However, these are merely examples of amemory medium and embodiments of the present invention are not limitedin these respects.

The term “programmable hardware element” is intended to include varioustypes of programmable hardware, reconfigurable hardware, programmablelogic, or field-programmable devices (FPDs), such as one or more FPGAs(Field Programmable Gate Arrays), or one or more PLDs (ProgrammableLogic Devices), such as one or more Simple PLDs (SPLDS) or one or moreComplex PLDs (CPLDs), or other types of programmable hardware. Aprogrammable hardware element may also be referred to as “reconfigurablelogic”. A programmable hardware element may be configured using ahardware configuration program. However, these are merely examples of aprogrammable hardware element and reconfigurable or programmable logic,and embodiments of the present invention are not limited in theserespects.

The term “program” is intended to have the full breadth of its ordinarymeaning. The term “program” includes 1) a software program which may bestored in a memory or memory medium and is executable by a processor or2) a hardware configuration program useable for configuring aprogrammable hardware element. However, these are merely examples of aprogram and embodiments of the present invention are not limited inthese respects.

The term “software program” is intended to have the full breadth of itsordinary meaning, and includes any type of program instructions, code,script and/or data, or combinations thereof, that may be stored in amemory medium and executed by a processor. Exemplary software programsinclude programs written in text-based programming languages, such as C,C++, Pascal, Fortran, Cobol, Java, assembly language, etc.; graphicalprograms (programs written in graphical programming languages); assemblylanguage programs; programs that have been compiled to machine language;scripts; and other types of executable software. A software program maycomprise two or more software programs that interoperate in some manner.However, these are merely examples of a software program and embodimentsof the present invention are not limited in these respects.

The term “hardware configuration program” is intended to include anetlist, bit file, or other type of program or data structure that canbe used to program or configure a programmable hardware element.However, these are merely examples of a hardware configuration programand embodiments of the present invention are not limited in theserespects.

The term “machine-readable” instructions as referred to herein relatesto expressions which may be understood by one or more machines forperforming one or more logical operations. For example, machine-readableinstructions may comprise instructions which are interpretable by aprocessor compiler for executing one or more operations on one or moredata objects. However, this is merely an example of machine-readableinstructions and embodiments of the present invention are not limited inthis respect.

The term “storage medium” as referred to herein relates to media capableof maintaining expressions which are perceivable by one or moremachines. For example, a storage medium may comprise one or more storagedevices for storing machine-readable instructions or data. Such storagedevices may comprise storage media such as, for example, optical,magnetic or semiconductor storage media. However, these are merelyexamples of a storage medium and embodiments of the present inventionare not limited in these respects.

The term “logic” as referred to herein relates to structure forperforming one or more logical operations. For example, logic maycomprise circuitry which provides one or more output signals based uponone or more input signals. Such circuitry may comprise a finite statemachine which receives a digital input and provides a digital output, orcircuitry which provides one or more analog output signals in responseto one or more analog input signals. Such circuitry may be provided inan application specific integrated circuit (ASIC) or FPGA. Also, logicmay comprise machine-readable instructions stored in a storage medium incombination with processing circuitry to execute such machine-readableinstructions. However, these are merely examples of structures which mayprovide logic and embodiments of the present invention are not limitedin this respect.

A “processing system” as discussed herein relates to a combination ofhardware and software resources for accomplishing computational tasks.However, this is merely an example of a processing system andembodiments of the present invention are not limited in this respect. A“host processing system” relates to a processing system which may beadapted to communicate with a “peripheral device.” For example, aperipheral device may provide inputs to or receive outputs from anapplication process hosted on the host processing system. However, theseare merely examples of a host processing system and a peripheral device,and embodiments of the present invention are not limited in theserespects.

A “communication network” as referred to herein relates to a pluralityof entities that may exchange data through a data transmission medium.In one example, each entity in the communication network may beassociated with an “address” that is used for transporting data to theentity according to a data communication protocol. However, this ismerely an example of a communication network and embodiments of thepresent invention are not limited in this respect.

An “Internet connection” as referred to herein relates a means foraccessing any one of several entities coupled to a communication networkknown as the “Internet.” The Internet comprises a networkinginfrastructure comprising a network of networks. An entity on theInternet may be associated with a “globally routable Internet Protocol(IP) address” which may be used for addressing data transmissionsaccording to an Internet Protocol. An Internet connection may beprovided by any one of several commercial Internet service providers(ISPs). An ISP may forward a message from a subscriber to any one ofseveral entities on the Internet according to a globally routable IPaddress associated with the entity. However, these are merely examplesof an Internet connection and embodiments of the present invention arenot limited in these respects.

A “local network” as referred to herein relates to a communicationnetwork having entities that communicate according to a locally defineddata communication protocol. For example, each entity in a local networkmay be associated with a “local address” which is unique among localaddresses allocated to entities in the local network. This may enableentities in the local network to communicate with one another using theallocated local addresses and the locally defined communicationprotocol. Using only the allocated local addresses and locally definedcommunication protocol, however, each entity in the local network may belimited to communicating with entities in the local network and may notbe capable of communicating with other entities in a largercommunication network that includes the local network. However, theseare merely examples of a local network and embodiments of the presentinvention are not limited in these respects.

A “gateway” as referred to herein relates to an entity in a localnetwork that is capable of communicating with other entities within oroutside of the local network. For example a gateway may be capable ofcommunicating with entities in the local network using allocated localaddresses according to a locally defined data communication protocol andalso capable of communicating with entities outside of the local networkusing a different addressing scheme or data communication protocol. Sucha gateway may also be capable of forwarding data communications betweenentities in the local network and entities outside of the local network.However, these are merely examples of a gateway and embodiments of thepresent invention are not limited in these respects.

The term “network element” as referred to herein represents a networkdevice such as a router, switch, gateway, or NAT (defined later herein)that is used to transmit a packet to another entity on the local networkor via an Internet connection. However, these are merely examples of anetwork element and embodiments of the present invention are not limitedin these respects.

The term “network protocol processing” as used herein refers to networkprocessing or processing in processing systems such as a communicationnetwork or local area network in which network processing isaccomplished with protocol processing such as, for example, TCP/IP(Transmission Control Protocol/lnternet Protocol) or other networkprotocol. However, these are merely examples of network protocolprocessing and embodiments of the present invention are not limited inthese respects.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the invention. Thus, the appearances ofthe phrases “in one embodiment” or “in an embodiment” in various placesthroughout this specification are not necessarily all referring to thesame embodiment. Furthermore, the particular features, structures, orcharacteristics may be combined in any suitable manner in one or moreembodiments.

The present invention may best be understood by analyzing two elementsof a wireless network, a node client element and a server element. Whencombined to form a whole, the node client element and the server elementare capable of measuring the per node packet loss for an ad hoc network.

Node Client Element: The node client element may be considered to be apacket generation utility that exists on multiple ad hoc wirelessconnected nodes. At any point in time, the nodes may generate networkpackets that are encoded with a unique identification for theoriginating node and the number of packets generated up to that point intime. The unique identifier may be used as the packet source identifierreceived by a server, but may not reflect the true source of the packet(as in the case of a NAT device, i.e., a “Network Address Translation”device). The node client element (sometimes referred to herein as“packet generation” utility) can be adjusted using a local or remoteuser interface such as a command line where adjustment commands aretyped by a user to, for example, increase or decrease the packet sizeand generation rate to better reflect network variations, networkvariations such as changes in network topology or packet transmissionchoices.

Server Element: In addition to the server element receiving the packetsfrom one of the node client elements, the server element may parse thereceived packet data, calculate the per-node packet loss of each nodeclient element by comparing the number of packets received and thenumber of packets sent, and may store that data in the server elementfor later use. The server element may also calculate and storeadditional data, such as last packet arrival time or duplicate packetcount.

A transmission medium may be tested with the assumption that thetransmission medium under test has uniform reliability from node tonode, regardless of the node location in the transmission medium. Asingle node of the network may test a communication link by acting as asingle node of the network, and assume that the measured packet losswill be consistent across all nodes of the transmission medium. However,depending on multiple factors, each node of the transmission medium mayhave different packet loss characteristics; in the present disclosurethese loss characteristics are tracked by individual node testing ofeach link of the transmission medium on a per-node basis.

An improved network configuration may be identified by measuring thepacket loss for any given or all nodes in the network. Further, bymeasuring the packet loss of a communication link at a given node, thenode may be adjusted to enhance or influence battery lifetime.

FIG. 1 illustrates an exemplary wireless network 100 of nodes 104 and aserver 102 operating according to an embodiment of the presentinvention. In other words, the wireless network 100 may form acommunication network, e.g., an ad hoc network. As stated, the wirelessnetwork 100 illustrates an ad hoc network of eleven nodes (also known as“entities” or “network elements”), ten of which are acting as clients,and at least one (marked “server”) acting as the server 102 (also knownas an “entity” or “network element”).

By “ad hoc” network, it is meant a communication network such as awireless network that is formed when one node is communicatively coupledto another node, the communication network possibly including local aswell as remote, such as across a gateway, communications. Arrowsrepresenting packet flow are shown and should be understood to representmulti-directional transmissions if required. For example, each node 104may act as a network element for other node(s) traffic, i.e., client 5may act to route packets from client 4 to client 9.

In the illustrated embodiment, in order to test packet loss on a pernode basis, each node 104 is assigned a unique identifier, which thenode 104 (sometimes referred to herein as the “client”) would use whengenerating packets. The server 102 may then identify the originationpoint of the packet (which may be different than the most recent sourceaddress of the packet) based upon the unique identifier. Each client mayalso maintain a count of the number of packets that the client hastransmitted, and encode that count into each packet that is subsequentlytransmitted.

In this environment, client 1, client 4 and client 7 may experience ahigher packet loss then client zero because each is connecting(multi-hopping) to the server 102 via client 5 while client 0 isconnecting directly (single hop) to the server 102. This packet loss maybe a result of unreliability in a wireless transmission medium; orbecause client 5's inability to receive a limited number of packets atany given time. Using the per-node packet loss tests, an administratormay be able to see which nodes are experiencing an excessive loss ofpackets and may be able to take corrective actions to alleviate theproblem.

To handle the reported losses, an administrator may re-position thenodes to reduce the hop distance between nodes one, four, and seven andthe server 102 or add more nodes to reduce the amount of traffic flowingthrough node five. Unlike prior art systems, overall mesh networkviability of the wireless network 100 is determined by measuring thepacket loss from each of the nodes 104 and the server 102.

FIG. 2 illustrates one embodiment of packet flow in the server 102 ofthe wireless network 100, and shows the flow of a packet once it entersthe server 102 and how the data of the packet is parsed, stored, anddisplayed. When a packet arrives 201, it may be stored for laterprocessing (in the packet cache 202), it may be processed upon receiptat the socket connection 203, or the server 102 may perform some otheraction which for purposes of understanding the present disclosure hasnot been described herein. If the packet is cached, the server 102 mayassociate an identifier with the out-of-order packets prior toprocessing the packets.

In process two 205, for each retrieved packet 206, the server 102compares the retrieved packet with the last N number of packets 208 thathave been received (stored in the packet history list 204) to determineif the packet is a duplicate packet. If the server 102 determines thatthe packet is a duplicate packet, the server 102 is able to discard theduplicate packet and process the next packet in the cache. The server102 may also track the number of duplicate packets that are beingreceived by the server which can be stored with the node hash element(not illustrated). The node hash element represents the information fora specific node 102, 104 in the wireless (or mesh) network 100. This isa data store and has no functionality other then to maintain a record ofits given node's information.

When a unique packet is found, the server 102 parses the packet 212, andthe server 102 retrieves the node identifier from the packet as well asretrieving the packet number from the packet. The server 102 thencalculates the packet loss 214 by comparing the packet number from theimmediately preceding packet received from that node 104 against thecurrent packet number. Using the difference between the two numbers, theserver 102 is able to determine the number of packets that have beenlost during packet transmission in the transmission medium. Anydifference greater than one is considered to be the lost packet count.The formula for calculating packet loss is:P _(k+1) =P _(k)+(C−L−1)where:

-   -   P_(K)=total packet loss calculated in a previous period    -   P_(K+1)=total packet loss calculated in a current period    -   C=packet count in the current period; and    -   L=packet count in the previous period.

The server 102 may stores the previous packet count and packet lossinformation. The server 102 may also store additional information suchas duplicate packet count, out-of-order packet count, last packetarrival time, or other relevant packet information that might be desiredor obtainable. The server 102 may store this information in a hash table(not shown) or other convenient programming utility. The server 102stores this packet information at either a fixed interval (e.g., onceevery five seconds, ten seconds, etc.) or until the packet cache 202 isexhausted.

The server 102 may cause node list information 220 to be directed tostandard out 218. Node list information 220 is updated 216 for eachpacket received by the server 102 with packet loss information and anyother information meant to be stored by the server 102. With intervalupdates, the option exists for the server 102 to reset the node list 220to a zero state to reflect, for example, a changing network topology.When the network topology changes during an interval, the server 102 mayshow the packet loss rate for only those nodes 104 whose packets wererecorded during the interval. Process two 205, as distinguished fromprocess three 207 described herein, may be considered to provide acumulative display of the node list information 220.

Unlike process two 205, in process three 207 an interval, rather thancumulative, display of node list information 220 is carried out. Inprocess three 207, the node list information 220 is generated in whichthe node list information 220 is updated periodically over an intervalin which a get node list command 230 is executed prior to printing thenode list to standard out 232. When the node list is reset 234, it isused as the node list 220 until the interval expires 236. The intervalexpires 236 when a particular amount of time passes that a user selectsfor an interval, i.e., “X” number of seconds (adjustable by the user).

In process three 207, the server 102 reads the node list 220 duringprocess three 207 and displays statistics that were recorded from thelast time that the server 102 read the node list 220. The server 102then resets the statistics (e.g., packets received, packets expected,etc.) back to zero, and continues with process three 207. Process three207 represents a user influenced interval display in order to compensatefor occasional discrepancies in packet transmissions in the wirelessnetwork 100. Process three 207 allows for a sampling of mesh viabilityover a specific period of time rather than the cumulative mesh viabilitythat is reported by default in process two 205.

The purpose of this recording in process two 205 and process three 207is to show that data may be captured by the server 102 and shown in atleast two separate ways. First, as a real time aggregate display inwhich the cumulative results of the packet loss measurement is reportedback to the server 102, and second, as a method to allow a person to seewhat the packet loss might be for a specific period of time. When aperson is able to see what the packet loss is for a specific period oftime, the person is able to see if a sudden packet loss in the wirelessnetwork 100 is a result of a transitory error in the packet flow of thenetwork 100, or a pattern of repeated packet loss that should beappropriately handled by a system administrator for the wireless network100.

While the invention has been described in terms of several embodiments,those of ordinary skill in the art should recognize that the inventionis not limited to the embodiments described, but can be practiced withmodification and alteration within the spirit and scope of the appendedclaims. The description is thus to be regarded as illustrative insteadof limiting.

1. A method comprising: measuring cumulative mesh network viabilitybased upon packet loss information calculated from packets transmittedfrom at least one of a plurality of nodes.
 2. The method of claim 1wherein the wireless network is an ad hoc wireless network.
 3. Themethod of claim 1 further comprising storing the packet loss informationat the at least one server.
 4. The method of claim 3 wherein saidstoring the packet loss information comprises network protocolprocessing a received packet upon receipt of the received packet at theat least one server.
 5. The method of claim 3 wherein said storing thereceived packet at the at least one server comprises processing thereceived packet at a time period subsequent to the arrival of thereceived packet at the server.
 6. The method of claim 3 wherein saidstoring the received packet at the at least one server comprisesassociating an identifier with the received packet prior to processingthe received packet.
 7. The method of claim 3 wherein said storing thereceived packet at the at least one server further comprises comparingthe packet with a plurality of previously received packets to determinewhether a duplicate packet had been transmitted.
 8. The method of claim7 wherein the at least one server discards the received packet inresponse to detecting that the received packet is a duplicate packetthat has been transmitted.
 9. A wireless network comprising: a pluralityof nodes configured to at least transmit packets in the wirelessnetwork; at least one server operably configured to calculate packetloss information in the wireless network during packet transmission fromat least one of the plurality of nodes such that overall mesh networkviability of the wireless network is measured in the wireless network;and a store for storing the packet loss information.
 10. The wirelessnetwork of claim 9 wherein the store for storing the packet lossinformation is at the at least one server.
 11. The wireless network ofclaim 9 wherein the store for storing the packet loss information isoperably configured for access at a future period of time.
 12. Thewireless network of claim 9 wherein the store for storing the packetloss information is operably configured for processing out-of-orderpackets.
 13. The wireless network of claim 9 wherein the server discardsthe packets.
 14. A wireless network comprising: a plurality of nodesconfigured to at least transmit packets in the wireless network; atleast one memory medium, the at least one memory medium having aninstruction set operably configured to calculate packet loss informationin the wireless network during packet transmission from at least one ofthe plurality of nodes in the wireless network such that overall meshnetwork viability of the wireless network is measured in the wirelessnetwork; and a store for storing the packet loss information.
 15. Thewireless network of claim 14 wherein the store for storing the packetloss information is at at least one server.
 16. The wireless network ofclaim 14 wherein the store for storing the packet loss information isoperably configured for access at a future period of time.
 17. Thewireless network of claim 14 wherein the store for storing the packetloss information is operably configured for processing out-of-orderpackets.
 18. The wireless network of claim 14 wherein the serverdiscards the packets when duplicate packets are detected.
 19. A memorymedium comprising: a set of instructions operably configured tocalculate packet loss information in a wireless network during packettransmission from at least one of a plurality of nodes in the wirelessnetwork such that overall mesh network viability of the wireless networkis measured.
 20. The memory medium of claim 19 wherein the packet lossinformation is stored in a store at at least one server in the wirelessnetwork.
 21. The memory medium of claim 19 wherein the packet lossinformation tracks packets regardless of an order that the packets arereceived at at least one server in the wireless network.
 22. An articlecomprising: a storage medium comprising machine-readable instructionsstored thereon to: calculate packet loss information in a wirelessnetwork during packet transmission from at least one of a plurality ofnodes in the wireless network such that overall mesh network viabilityof the wireless network is measured.
 23. The article of claim 22,wherein the wireless network comprises an ad hoc wireless network. 24.The article of claim 22, wherein the storage medium further comprisesmachine-readable instructions stored thereon to: store the packet lossinformation at at least one server for access at a future period oftime.
 25. The article of claim 24, wherein the storage medium furthercomprises machine-readable instructions stored thereon to: process areceived packet upon receipt of the received packet at the at least oneserver.
 26. The article of claim 24, wherein the storage medium furthercomprises machine-readable instructions stored thereon to: process thereceived packet at a time period subsequent to the arrival of thereceived packet at the at least one server.
 27. The article of claim 24,wherein the storage medium further comprises machine-readableinstructions stored thereon to: associate an identifier with thereceived packet prior to processing the received packet.
 28. The articleof claim 24, wherein the storage medium further comprisesmachine-readable instructions stored thereon to: compare the packet witha plurality of previously received packets to determine if duplicatepackets have been transmitted.
 29. The article of claim 28, wherein thestorage medium further comprises machine-readable instructions storedthereon to: cause the at least one server to discard the received packetin response to detecting that the received packet is a duplicate packetthat has been transmitted.
 30. A system comprising: a plurality of nodesconfigured to at least transmit packets in a wireless network; at leastone server operably configured to calculate packet loss information inthe wireless network during packet transmission from at least one of theplurality of nodes such that overall mesh network viability of thewireless network is measured in the wireless network, the at least oneserver having an ethernet adapter for wired communications; and a storefor storing the packet loss information.
 31. The method of claim 2wherein mesh network viability is the cumulative packet loss in the adhoc wireless network.
 32. The method of claim 3 where said storing thepacket loss information at the at least one server is for access at afuture period of time.